python的set集合学习（七）

在python中，set集合是一个无序并且不重复的元素集合，它的关键字是set，依然按照之前的思维方式，我们定义一个set集合，来看它的类所具备的功能以及对象功能的详细信息，这样的目的很简单，很多时候，我们不可能把字典，列表，元组，set集合类的方法都记得那么的清楚，但是使用的时候，我们可以通过dir()和help()来获取它的详细的信息，来实现自己所要实现的东西，OK，见如下的代码：

#!/usr/bin/env python 
#-*- coding:utf-8 -*-

s=set()
print u'set对象类的功能为:',dir(s)
print u'set对象的详细信息:',help(type(s))

见执行如上的代码后输出的信息：

C:\Python27\python.exe D:/git/Python/FullStack/share/setTest.py

set对象类的功能为: ['__and__', '__class__', '__cmp__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__iand__', '__init__', '__ior__', '__isub__', '__iter__', '__ixor__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__or__', '__rand__', '__reduce__', '__reduce_ex__', '__repr__', '__ror__', '__rsub__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__xor__', 'add', 'clear', 'copy', 'difference', 'difference_update', 'discard', 'intersection', 'intersection_update', 'isdisjoint', 'issubset', 'issuperset', 'pop', 'remove', 'symmetric_difference', 'symmetric_difference_update', 'union', 'update']

set对象的详细信息:Help on class set in module __builtin__:

class set(object)

| set() -> new empty set object

| set(iterable) -> new set object

|

| Build an unordered collection of unique elements.

|

| Methods defined here:

|

| __and__(...)

| x.__and__(y) <==> x&y

|

| __cmp__(...)

| x.__cmp__(y) <==> cmp(x,y)

|

| __contains__(...)

| x.__contains__(y) <==> y in x.

|

| __eq__(...)

| x.__eq__(y) <==> x==y

|

| __ge__(...)

| x.__ge__(y) <==> x>=y

|

| __getattribute__(...)

| x.__getattribute__('name') <==> x.name

|

| __gt__(...)

| x.__gt__(y) <==> x>y

|

| __iand__(...)

| x.__iand__(y) <==> x&=y

|

| __init__(...)

| x.__init__(...) initializes x; see help(type(x)) for signature

|

| __ior__(...)

| x.__ior__(y) <==> x|=y

|

| __isub__(...)

| x.__isub__(y) <==> x-=y

|

| __iter__(...)

| x.__iter__() <==> iter(x)

|

| __ixor__(...)

| x.__ixor__(y) <==> x^=y

|

| __le__(...)

| x.__le__(y) <==> x<=y

|

| __len__(...)

| x.__len__() <==> len(x)

|

| __lt__(...)

| x.__lt__(y) <==> x<y

|

| __ne__(...)

| x.__ne__(y) <==> x!=y

|

| __or__(...)

| x.__or__(y) <==> x|y

|

| __rand__(...)

| x.__rand__(y) <==> y&x

|

| __reduce__(...)

| Return state information for pickling.

|

| __repr__(...)

| x.__repr__() <==> repr(x)

|

| __ror__(...)

| x.__ror__(y) <==> y|x

|

| __rsub__(...)

| x.__rsub__(y) <==> y-x

|

| __rxor__(...)

| x.__rxor__(y) <==> y^x

|

| __sizeof__(...)

| S.__sizeof__() -> size of S in memory, in bytes

|

| __sub__(...)

| x.__sub__(y) <==> x-y

|

| __xor__(...)

| x.__xor__(y) <==> x^y

|

| add(...)

| Add an element to a set.

|

| This has no effect if the element is already present.

|

| clear(...)

| Remove all elements from this set.

|

| copy(...)

| Return a shallow copy of a set.

|

| difference(...)

| Return the difference of two or more sets as a new set.

|

| (i.e. all elements that are in this set but not the others.)

|

| difference_update(...)

| Remove all elements of another set from this set.

|

| discard(...)

| Remove an element from a set if it is a member.

|

| If the element is not a member, do nothing.

|

| intersection(...)

| Return the intersection of two or more sets as a new set.

|

| (i.e. elements that are common to all of the sets.)

|

| intersection_update(...)

| Update a set with the intersection of itself and another.

|

| isdisjoint(...)

| Return True if two sets have a null intersection.

|

| issubset(...)

| Report whether another set contains this set.

|

| issuperset(...)

| Report whether this set contains another set.

|

| pop(...)

| Remove and return an arbitrary set element.

| Raises KeyError if the set is empty.

|

| remove(...)

| Remove an element from a set; it must be a member.

|

| If the element is not a member, raise a KeyError.

|

| symmetric_difference(...)

| Return the symmetric difference of two sets as a new set.

|

| (i.e. all elements that are in exactly one of the sets.)

|

| symmetric_difference_update(...)

| Update a set with the symmetric difference of itself and another.

|

| union(...)

| Return the union of sets as a new set.

|

| (i.e. all elements that are in either set.)

|

| update(...)

| Update a set with the union of itself and others.

|

| ----------------------------------------------------------------------

| Data and other attributes defined here:

|

| __hash__ = None

|

| __new__ = <built-in method __new__ of type object>

| T.__new__(S, ...) -> a new object with type S, a subtype of T

None

Process finished with exit code 0

依据如上的详细信息可以看到，在新式类set中，有很多的方法，那么这里，我们就学习部分经常使用的方法，其他的方法，如果不清楚的，可以看它的注释，有详细的解释。经常使用的方法案例代码为：

#!/usr/bin/env python 
#-*- coding:utf-8 -*-

s=set()
#集合插入数据
s.add('wuya')
s.add('admin')
print u'见插入数据后的集合内容:',s,type(s)

#把列表转换为集合
list1=[11,22,33,44,55]
print u'列表list1转换为集合后:',set(list1),type(set(list1))

#查看b集合存在,a集合不存在的情况
b={1,2,3,4,5}
a={6,7,8,9,0,1}
print u'查看b集合存在,a集合不存在的内容:',b.difference(a)
print u'移除指定的集合，不存在不会出现错误:',b.discard('wuya')
print u'查看集合a,b都存在的值:',a.intersection(b)
#没有交集，返回True,存在交集返回False
print u'判断集合a,b是否存在交集:',a.isdisjoint(b)
print u'移除集合的元素并且获取值:',a.pop()
print u'获取a,b集合的并集:',a.union(b)
b.update(a)
print u'集合b更新后的内容为:',b